Once the desired ringtone has been downloaded, it will give you the option to save as. You will then be given the option to select whether you want to set it as a text notification, email notification and etc. You can get tones from the media store as well as the android market.
if you have music loaded on your phone like I do then pick out a particular song that you want and use the long touch method(that is hold it for several seconds) on that song. A screen will pop up and give youseveral selections to chose from. Mainly you will be using the set as feature. When the se as screen pops up, it will have 3 choices voice call ring tone,caller ring tone or alarm tone. Make your choice. If you use the caller ringtone, then choose the contact you want for that paricular ringtone. Please make note that when that is done, that ringtone will be listed in the ringtone catagory. Then if you want to use that song(s) foyour notifications, then go to ringtone and it should be listed and then choose that of your tone. Hope that will help you